This invention relates to recording media which can be imaged by exposure to actinic radiation. More particularly, the invention relates to articles capable of being used for high resolution recording based on the use of photochromic axiridines which allow the image-forming operation to be reversible, i.e. the recorded image may be erased.
Many conventional imaging materials undergo irreversible changes when exposed to actinic radiation. Thus, erasure is impossible without physical destruction of the image itself. Additionally, in many instances, the image formed is latent, and subsequent development is necessary.
Photochromes are compounds which change color reversibly on exposure to actinic radiation. Such direct-developing photochromic materials traditionally suffer the limitation that images produced from systems containing these materials have very little stability, i.e. the image will fade spontaneously within a few minutes or hours at room temperature.
It has now been ascertained that particularly defined photochromic aziridine compounds, vapor coated on a substrate, can be utilized for high resolution, long term recording wherein the recorded image may be erased and information may be added, the film may be re-used, etc. The films can be utilized in data recording applications such as video disc or microfiche, especially in conjunction with high density data recording. Besides being direct developing, such media can be updated or erased. The films can further be used as intermediates in photographic and/or copying processes and as proofing materials.
In Schleigh et al, U.S. Pat. No. 3,894,874, there is described the use of aziridines in photoreductive imaging. A reducible, image-forming compound is combined with the photochromic aziridine in a binder on a substrate to form a radiation-sensitive layer. Upon exposure to actinic radiation, followed by heating, an image may be obtained. Furthermore, partly crystalline and partly crystallographically aligned photochromic aziridines and oxiranes are disclosed as having utility in windshields, sunglasses, and light switching devices in U.S. Pat. No. 3,964,823.
It has now been found that by vapor depositing the hereinafter-defined photochromic aziridines onto a substrate, a high resolution photochromic thin film can be produced. It has further been found that by covering this film with certain materials, the high resolution can be maintained. It has further been found that by utilizing an oxygen barrier material to cover the thin aziridine film, the lifetime of the image formed by exposure to actinic radiation can be increased at least a thousand times more than that of the photochromic aziridine in oxygen or air.